Relationship between Inflammatory Markers (IL-6, IL-10, TNF-alpha, CRP), Physical Performance Measures and Ethnic Differences

Title: Relationship between Inflammatory Markers (IL-6, IL-10, TNF-alpha, CRP), Physical Performance Measures and Ethnic Differences

Authors: Sebastian Meza, OMS-II, Yein Lee, DO, MMS, Blake Campbell, OMS-II, Paige Hurt, OMS-II, Melissa Petersen, PhD, Rita M. Patterson, PhD

Background: Hispanics remain highly underrepresented in Alzheimer's Disease (AD) research. This study explores the possible relationship between the inflammatory markers commonly studied in AD and Physical Performance Tests for gait and mobility in patients self-identified as Mexican American and Non-Hispanic White. In addition, this study will elaborate on the variations found in this biomarker-functional measure relationship among different ethnic groups.

Methods: Publicly available data were analyzed on n=1705 participants (n=890 Mexican Americans; n=815 Non-Hispanic Whites) from the Health and Aging Brain Study- Health Disparities (HABS-HD). Participants completed a full study protocol including a clinical interview, cognitive testing, blood work, and functional exam. Targeted proteomics were analyzed on a Meso Scale Discovery Platform using ECL techniques and included markers of inflammation (CRP, IL6, IL10, TNFα). The functional testing included the following measures: Tug Time Test, Balance Test, Gait Speed Test, and Chair Stand Test. Linear regression models were run with select inflammatory markers (CRP, IL6, IL10, and TNFα) as the independent variables and the different musculoskeletal functional tests as the dependent variables. The analyses were conducted in a split method to compare the output by ethnic group (Hispanic and Non-Hispanic White).

Results: This study showed that physical performance measures had a more direct relationship with the inflammatory markers in the Mexican American group as compared to the Non-Hispanic White group. Among Mexican Americans, all physical performance measures were found to be significantly related to IL-6 and TNFα while Gait speed was found to be significantly related to CRP, IL-6, IL-10 and TNFα. Although non-significant, there was a trend for the relationship between IL-10 with both Tug Time and Total Balance Test. Among Non-Hispanic Whites, IL-10 was found to be significantly related to the functional measure of Total Balance while TNFα was significantly related to the Chair Standing Test. IL-6 was found to be significantly related to all physical performance measures. CRP was not found to be related to any of the functional/physical performance tests.

Discussion: The results demonstrate differences in the relationship between inflammatory markers and physical performance measures across ethnic groups. Our findings support the research community's need to focus more on differences among ethnic groups. Surprisingly, CRP was not found to be related to physical performance measures (in the Non-Hispanic White group) despite being a widely used inflammatory marker in clinical settings. To examine the potential utility for understanding the impact of inflammatory markers on functional abilities and the potential application for clinical use, future work is planned to look at this relationship among those with AD.